In this article we will discuss about the chemical composition of chromatin. Chromatin is composed of DNA (30-40%), RNA (1-10%) and proteins (50-60%). These constituents vary in different organisms and even in the different tissues of the same species (Table 8.2). Even in the same call, the proportions of DNA, RNA and proteins vary with the stage of cell cycle. [...]
The following points highlight the top four models proposed for chromosome structure. The models are: 1. Molecular Model 2. Multi-Stranded Model or Polyneme Chromosome Model 3. General Chromosome Model 4. Folded Fibre Model. Chromosome Structure: Model # 1. Molecular Model: This model of chromosome structure was proposed by Taylor and coworkers in 1957, 1963 and is based on the semiconservative [...]
In this article we will discuss about the changes in chromatin structure during transcription. Displacement of nucleosomes: During transcription, some changes in the chromatin structure occur in the region of transcription. RNA polymerase is comparatively larger in size than the nucleosomes. The molecular weight of RNA polymerase is about 5,00,000 Daltons, while that of nucleosome is about 2,60,000 Daltons. Lewin [...]